1. Technical Field
The present disclosure relates generally to light guides for transferring illuminating light from a light source to surgical instrumentation, and, more particularly, to a flexible liquid light guide for transmitting light in the visible spectral range to an endoscope.
2. Background of Related Art
In endoscopic surgical procedures, illuminating light is typically transmitted from an external light source to an endoscope where the light is then transmitted via an illuminating system incorporated within the endoscope to the body cavity to be viewed. A conventional light cable for providing the endoscope with illumination is a fiber optic light bundle having a plurality of optical fibers of glass or optical plastic. The fiber optic bundle is connected at one end to the light source and at the other end to an inlet port of the endoscope. This system is typically referred to as a fiber optic light guide.
A significant drawback of fiber optic light guides involves the degradation of the fibers when used over extended periods of time. This degradation is due in part to the repetitive flexing the light guide experiences when the bundle is initially connected to the light source and the endoscope, and during maneuvering about the operative site in the course of the surgical procedure. Since fiber optic light guides are relatively expensive and are intended to be reused, the light guides are typically employed in many surgical procedures over a substantial period of time. Consequently, the light transferring quality of the fiber optic light guide tends to gradually degrade to a point where the level of light emitted by the fiber optic bundle is substantially less than the light initially received from the light source.
One attempted solution to this problem has been to substitute liquids for fiber optic bundles. Examples of such liquid light guides are described in U.S. Pat. Nos. 3,740,113; 3,920,980; 3,995,934; 4,045,119; 4,907,133 and 5,165,773. In the light guides suggested in these patents, a liquid transmissive fluid is encapsulated within a flexible tube which is closed off at each end with a transparent end plug. Light entering the guide is transmitted via the fluid to the endoscope. Conventional liquid transmissive fluids include nitrobenzene, camphor oil, linseed oil, chlorobenzene, castor oil and benzyl alcohol.
Conventional liquid light guides such as those described in the above-mentioned patents have their own drawbacks and limitations. In particular, these light guides are subject to leakage particularly through the seals created between the end plugs and the end portions of the flexible tube. This is particularly true at the light source entry side of the light guide where the heat generated by the light source affects the integrity of the seal, e.g., may degrade the adhesive seals attaching the end plug to the flexible tube. The heat may also degrade the liquid light transmissive material and introduce optical defects such as bubble therein. Another disadvantage with known liquid light guides include their relative expense.
Accordingly, the present disclosure is directed to a low cost liquid light guide capable of efficiently supplying an endoscope with illuminating light particularly in the visible spectral range and one which incorporates structure which positively seals the end portions of the light guide cable to prevent leakage of the light transmissive fluid contained therein. Manufacture and assembly of the light guide is relatively inexpensive in comparison to fiber type cables.